Repair faulty sensor or remedy coolant leak

Complementary Modification:

Replace radiator hose

M54 and 8-cylinder engines: Belt driven coolant pump bolted to the front of the engine block.

N52 and N54 engines: Electric coolant pump bolted to the right front of the engine block.

Electric cooling fan attached to rear of radiator. The cooling fan is controlled by the engine control module (ECM) via an output final stage.

Automatic transmission cooler (heat exchanger).

Heater valve and heater core (for climate control).

Coolant level sensor inside expansion tank.

Coolant temperature sensor at cylinder head.

Radiator outlet temperature sensor

Coolant hose and lines.

The radiator outlet temperature sensor, located in the right side radiator hose, monitors coolant temperature as it leaves the radiator. The sensor reading is used by the engine management system (DME) to determine when the electric cooling fan is activated. The DME uses other inputs as well to control cooling fan operation and speed: coolant temperature at the cylinder head and AC operation.

The radiator outlet temperature sensor can fail electrically; a fault code will be stored and the MIL (malfunction indicator lamp) will be illuminated. The sensor can also leak coolant from the sensor sealing O-ring. I have replaced this sensor and soon after developed a leak at the lower radiator hose. If it's in your budget, replace the lower radiator hose also as preventative maintenance. Replacing the radiator outlet temperature sensor is a snap and can be done working above the engine on the right side of the radiator.

In this article I will describe how to replace the radiator outlet temperature sensor. Be sure to work with a cool engine and confirm the cooling system lacks pressure before opening the cooling system.

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability.

Vehicle models change and evolve, as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

The radiator outlet temperature sensor (green arrow) might be the cause of a hard to find coolant leak. The sensor is mounted in a plastic section of the right side radiator hose. There is a sealing O-ring that normally prevents leaks in the system. Over time, this O-ring fails and creates a coolant leak. At first, it will be a small leak. You may notice a small amount of coolant under the right side of your vehicle or the coolant reservoir coolant level slowly dropping. This photo shows the beginning of a failing O-ring. You can see coolant seeping out through the sensor mounting bung (note wet area around sensor). If you have a small, yet hard to locate coolant leak, start by inspecting this sensor. The photo shows a sensor on a 6-cylinder E60.

This photo shows the sensor on an 8-cylinder E60 model. You can see the sensor is the same, the hose changes slightly. Clean the area on the hose around the sensor. You want to remove any dirt or debris that could go into the sensor mounting bung when the sensor is removed. This goes for all models.

To remove the sensor from the hose, squeeze the plastic locking tabs on the sensor (green arrows) and pull the sensor out of the radiator hose. Be prepared to catch any excess dripping coolant in a container when you pull the sensor out of the hose. I like to keep my drain pan under the area of the hose. To install the new sensor, lubricate the sensor O-ring with clean engine coolant. Then push it into the radiator hose until both plastic mounting tabs engage. Then connect the electrical connector and reassemble the intake air duct and cooling fan. Fill and bleed the cooling system.

If you suspect the sensor is good and the wiring or voltage to be faulty, disconnect the electrical sensor as noted above. Using a DVOM check the voltage to the sensor. Pin 1 should have 5 volts. Pin 2 should have close to zero volts. If your voltage readings do not match, you may have a faulty wire or control module. Consult the most current wiring diagram for your vehicle.

Comments: Thank You, it took me only five mins thanks to your photos. I wasnt sure what to do with the wire clip. Im shopping here from now on :D

December 16, 2016

Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts

Andy

Comments: Hi I'm wondering if you could help me with my 2007 525xi bmw? When I first start the car the high speed coolant fan will come on then I shut off car and restart it will stay off for awhile and I don't have any heat. Sometimes I can hear fan revin from low to high and once in awhile the computer will tell me shut the engine off its to hot I do and start it right back up and it's fine. And the engine compartment is cool and no steam, on top of that I had a scan done and there's no codes at all, please help confused thank you Andy

November 15, 2016

Followup from the Pelican Staff: There may be an issue with the coolant pump. If so, the fan will come on high. Could also be a faulty fan. You should start by checking the vehicle for fault codes. - Nick at Pelican Parts

Patrick

Comments: Edit: codes are 002e81 and 002e84. Sorry about that.

April 10, 2016

Followup from the Pelican Staff: Got it. - Nick at Pelican Parts

Patrick

Comments: Hi. I'm getting codes 002e81 and 002e81 amd don't know if it's the sensor or the electric pump. Any help is appreciated!

April 10, 2016

Followup from the Pelican Staff: I think those codes are for the pump, not running. - Nick at Pelican Parts

Vin

Comments: Hi, can you please advice me for this issue, what do I need to change? The hose or only the O-ring?

December 9, 2015

Followup from the Pelican Staff: The hose, as the O-ring is not available separately. Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts

Paul

Comments: Hi Nick,
Trust you are well.
I bought the temperature water/oil sensor and installed it however there is no difference I do not think this is the problem, I believe the problem is the thermostat your part number 11-53-7-549-476 BOE.
Do you ship to South Africa?

Thanking you

Kind regards

Paul

November 6, 2015

Followup from the Pelican Staff: I am not sure if we ship there. To be sure, Give our parts specialists a call at 1-310-626-8765
- Nick at Pelican Parts

Paul

Comments: Hi Nick

Thank you

Kind regards

Paul

November 4, 2015

Followup from the Pelican Staff: No problem. - Nick at Pelican Parts

Paul

Comments: Hi Nick, thank you for your help my car is not like those in the pictures however my fault I should have provided you with my vehicle's VIN number

It is WBANU52088CZ87815

Please tell me where this coolant sensor is.

Thanking you

Kind regards

Paul

November 4, 2015

Followup from the Pelican Staff: There is one in the lower radiator hose, as described in article. And one in the front of the cylinder head. As I mentioned. - Nick at Pelican Parts

Paul

Comments: Hi, can you please tell or indicate to me where I will find the coolant temperature sensor on a BMW 525i e60 2008 model and what will this sensor cost. I had a diagnosis conducted and it came up with a 2EE0 error code. It stated coolant temperature sensor.
What will I need to change this, can I do this myself, I know some mechanical work.

Thanking you in advance

November 3, 2015

Followup from the Pelican Staff: The coolant sensor is in the cylinder head, left front. Check if the sensor is faulty or connector is bad. - Nick at Pelican Parts

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